diff --git a/.pi/hooks/test-command.ts b/.pi/hooks/test-command.ts
index 52382d85..7f737498 100644
--- a/.pi/hooks/test-command.ts
+++ b/.pi/hooks/test-command.ts
@@ -2,7 +2,7 @@
  * Test hook demonstrating custom commands, message rendering, and before_agent_start.
  */
 import type { BeforeAgentStartEvent, HookAPI } from "@mariozechner/pi-coding-agent";
-import { Box, Text } from "@mariozechner/pi-tui";
+import { Box, Spacer, Text } from "@mariozechner/pi-tui";
 
 export default function (pi: HookAPI) {
 	// Track whether injection is enabled
@@ -10,20 +10,22 @@ export default function (pi: HookAPI) {
 
 	// Register a custom message renderer for our "test-info" type
 	pi.registerMessageRenderer("test-info", (message, options, theme) => {
-		const box = new Box(0, 0, (t) => theme.bg("customMessageBg", t));
+		const box = new Box(1, 1, (t) => theme.bg("customMessageBg", t));
 
 		const label = theme.fg("success", "[TEST INFO]");
 		box.addChild(new Text(label, 0, 0));
+		box.addChild(new Spacer(1));
 
 		const content =
 			typeof message.content === "string"
 				? message.content
 				: message.content.map((c) => (c.type === "text" ? c.text : "[image]")).join("");
 
-		box.addChild(new Text(theme.fg("text", content), 0, 1));
+		box.addChild(new Text(theme.fg("text", content), 0, 0));
 
 		if (options.expanded && message.details) {
-			box.addChild(new Text(theme.fg("dim", `Details: ${JSON.stringify(message.details)}`), 0, 2));
+			box.addChild(new Spacer(1));
+			box.addChild(new Text(theme.fg("dim", `Details: ${JSON.stringify(message.details)}`), 0, 0));
 		}
 
 		return box;
diff --git a/packages/coding-agent/src/core/hooks/index.ts b/packages/coding-agent/src/core/hooks/index.ts
index 6f34fe00..395d15e0 100644
--- a/packages/coding-agent/src/core/hooks/index.ts
+++ b/packages/coding-agent/src/core/hooks/index.ts
@@ -33,6 +33,7 @@ export type {
 	HookMessageRenderOptions,
 	HookUIContext,
 	LsToolResultEvent,
+	ReadonlySessionManager,
 	ReadToolResultEvent,
 	RegisteredCommand,
 	SessionEvent,
diff --git a/packages/coding-agent/src/core/hooks/types.ts b/packages/coding-agent/src/core/hooks/types.ts
index fa753b7e..e97e20e0 100644
--- a/packages/coding-agent/src/core/hooks/types.ts
+++ b/packages/coding-agent/src/core/hooks/types.ts
@@ -13,7 +13,34 @@ import type { CompactionPreparation, CompactionResult } from "../compaction.js";
 import type { ExecOptions, ExecResult } from "../exec.js";
 import type { HookMessage } from "../messages.js";
 import type { ModelRegistry } from "../model-registry.js";
-import type { CompactionEntry, SessionManager } from "../session-manager.js";
+import type {
+	CompactionEntry,
+	SessionEntry,
+	SessionHeader,
+	SessionManager,
+	SessionTreeNode,
+} from "../session-manager.js";
+
+/**
+ * Read-only view of SessionManager for hooks.
+ * Hooks should use pi.sendMessage() and pi.appendEntry() for writes.
+ */
+export type ReadonlySessionManager = Pick<
+	SessionManager,
+	| "getCwd"
+	| "getSessionDir"
+	| "getSessionId"
+	| "getSessionFile"
+	| "getLeafUuid"
+	| "getLeafEntry"
+	| "getEntry"
+	| "getLabel"
+	| "getPath"
+	| "getHeader"
+	| "getEntries"
+	| "getTree"
+>;
+
 import type { EditToolDetails } from "../tools/edit.js";
 import type {
 	BashToolDetails,
@@ -76,8 +103,8 @@ export interface HookEventContext {
 	hasUI: boolean;
 	/** Current working directory */
 	cwd: string;
-	/** Session manager instance - use for entries, session file, etc. */
-	sessionManager: SessionManager;
+	/** Session manager (read-only) - use pi.sendMessage()/pi.appendEntry() for writes */
+	sessionManager: ReadonlySessionManager;
 	/** Model registry - use for API key resolution and model retrieval */
 	modelRegistry: ModelRegistry;
 }
@@ -430,8 +457,8 @@ export interface HookCommandContext {
 	hasUI: boolean;
 	/** Current working directory */
 	cwd: string;
-	/** Session manager for reading/writing session entries */
-	sessionManager: SessionManager;
+	/** Session manager (read-only) - use pi.sendMessage()/pi.appendEntry() for writes */
+	sessionManager: ReadonlySessionManager;
 	/** Model registry for API keys */
 	modelRegistry: ModelRegistry;
 }